1. Field of the Invention
This specification relates to an apparatus for coupling a reflex mirror, and more particularly, to an apparatus for coupling a reflex mirror using an adhesive when mounting, as technology applied to mount a reflex mirror in a reflecting optical system of a large aperture.
2. Background of the Invention
In the conventional art, a reflex mirror formed of a material having a small thermal expansion such as Zerodur is assembled by being directly adhered to a mirror fixation device (MFD) formed of Invar. In this case, the following characteristics may be revealed.
Firstly, if thermal expansion coefficients of the reflex mirror and the MFD are different from each other, when temperature rising or temperature fall from a refining temperature occurs, deformation of the MFD due to the difference in the thermal expansion coefficients is transmitted to the reflex mirror, thereby degrading an optical performance. Such a phenomenon emerges even when deformation of several nm occurs. Further, when mounting the MFD to the reflex mirror, assembly processes become difficult due to a complicated shape of the MFD. An adhesion thickness, filling an adhesive in an adhesion part, and a precise adhesion position are important. Therefore, an adhesion shape is required to be simpler.
In the conventional art, when mounting the MFD to the aforementioned reflex mirror, the following problems may be caused.
Firstly, a stress is generated due to a difference in thermal expansion coefficients between the reflex mirror and the MFD. The stress is more increased as an adhesion surface has a longer length. A difference in contraction or expansion of the adhesion surface causes a curved shape of the reflex mirror.
Secondly, adhesion processes become difficult due to a low workability to mount the MFD to the reflex mirror (SiC reflex mirror). That is, it is difficult to fill an adhesive in the adhesion surface, and to control an adhesive thickness (generally, 0.05˜0.2 mm) and an adhesion position accuracy (direction, angle, position, thickness deviation).